There is no shortage of low to mid range restaurants everywhere in Tokyo and the majority serve very tasty food. If you're on a budget, the key is to take advantage of the lunch specials, where you could try a meal at a high end restaurant for as little as $25. For dinner you could then have simpler meals at a noodle shop or curry place for under $10. It's actually snacks and drinks during the day that easily add $5 here and there to your budget. The top floors of department stores usually have mid range reataurants with displays of the food on offer from tonkatsu to western food.